The present invention relates to a process for recovering a titanium dioxide product from a titanium oxide-containing roasted mass, and, more particularly, to a process improvement for recovering a titanium dioxide product from a roasted mass by exploiting an organic acid.
Iron oxides are present in many mineral ores such as mineral ores of chromium, titanium and copper. The removal of iron from these ores is essential for the extraction of the metal and its oxides (Sibum H (1997) Titanium Handbook of Extractive Metallurgy, Weinheim, Wiley-VCH). Various techniques for the removal of iron from the mineral ores have been exploited including reduction roasting, smelting and acid leaching in concentrated hydrochloric acid (see Gueguin M and Cardarelli F (2007) “Chemistry and mineralogy of titania-rich slags. Part 1—Hemo-ilmenite, sulphate, and upgraded titania slags” Mineral Processing and Extractive Metallurgy Review 28(1):1-58; Kahn J A (1984). “Non-Rutile Feedstocks for the Production of Titanium” Journal of Metals 36(7):33-38; and Lasheen T A I (2005). “Chemical beneficiation of Rosetta ilmenite by direct reduction leaching” Hydrometallurgy 76:123-129). However, these techniques are not very efficient in removing iron compounds and they can generate toxic waste (Sibum [supra]; and Doan P (2003). Sustainable development in TiO2 industry: Challenges and Opportunities. TiO2 intertech Miami, Fla.).
WO-A-2005/028369 discloses the recovery of titanium dioxide from a roasted mass using hot water to produce an insoluble residue in aqueous solution. Adding to the aqueous solution a source of alkalinity causes the selective separation of a fine precipitate from which may be recovered metal values including iron compounds. Metal values including iron compounds may also be recovered from the aqueous solution by acidification with a weak organic acid. The insoluble residue may be acid leached in an inorganic acid to remove zirconium, niobium, uranium and thorium compounds.
Iron compounds may be dissolved by treatment with organic acids, such as oxalic acid. Studies have been performed on the dissolution of hematite in oxalic acid (see Panias D Taxiarchou M Douni I Paspaliaris I and Kontopoulos A (1996). “Dissolution of hematite in acidic oxalate solutions: The effect of ferrous ions addition” Hydrometallurgy 43(1-3):219-230) and ascorbic acid (see Suter D, Banwart S and Stumm W (1991) “Dissolution of Hydrous Iron(Iii) Oxides by Reductive Mechanisms” Langmuir 7(4):809-813; and Banwart S, Davies S and Stumm W (1989). “The Role of Oxalate in Accelerating the Reductive Dissolution of Hematite (Alpha-Fe2O3) by Ascorbate” Colloids and Surfaces 39(4):303-309).
The present invention seeks to improve the recovery of a titanium dioxide product from a titanium oxide-containing roasted mass by exploiting an organic acid to effectively remove iron species (e.g., iron oxide) and alkali metal or alkaline earth metal species from the roasted titanium mineral by leaching.